1. Field of the Invention
The present invention relates to a bandwidth control method and a bandwidth control system in a network that interconnects by way of a plurality of trunk nodes each of a plurality of subscriber nodes that in turn accommodate a plurality of subscribers.
2. Description of the Related Art
RSVP (ReSource reservation Protocol) has been used as a communication control method for reserving bandwidth. In this communication control method, a bandwidth request (a request to reserve a transmission bandwidth) from a terminal is transmitted by way of, for example, an interposed router to the server that is the communication partner. Upon receiving the bandwidth request from the terminal, the interposed router transfers the request on to the next router while reserving a transmission bandwidth on the path. In this way, the entire transmission bandwidth on the path is reserved from the terminal to the server. Upon receiving the request signal from the terminal, the server determines whether acceptance is possible, and if acceptance is possible, sends a response signal indicating this state on the path for which the transmission bandwidth is reserved. This response signal follows the path taken by the request signal to reach the terminal at which the request originated.
Another method is a bandwidth reserving method used in an ATM (A synchronous Transfer Mode) network. Explanation of this method is presented with reference to a typical network shown in FIG. 1.
The network shown in FIG. 1 is made up of subscribers 11-13, 21-23, 31-33, and 41-43 (for example, residential and company subscriber servers); subscriber nodes 10, 20, 30, and 40 that accommodate these subscribers; and trunk nodes 50, 60, 70, and 80 that connect these subscriber nodes to each other.
Subscribers 11-13 are accommodated within subscriber node 10, subscribers 21-23 are accommodated within subscriber node 20, subscribers 31-33 are accommodated within subscriber node 30, and subscribers 41-43 are accommodated within subscriber node 40. Subscriber nodes 10 and 20 are link ed to each other by way of trunk node 50, subscriber nodes 30 and 40 are linked to each other by way of trunk node 60, and trunk nodes 50 and 60 are linked to each other by way of trunk nodes 70 and 80.
As an example, when guaranteeing a line of bandwidth Wa from subscriber node 10 to subscriber node 40 by the bandwidth control of the prior art, a virtual channel of bandwidth Wa is set at subscriber node 10 on each of links (trunk line) 51, 75, 78, 86, and 64 up to subscriber node 40. In this way, bandwidth is guaranteed by placing in correspondence subscriber node pairs (pairs of transmission source subscriber nodes and destination subscriber nodes) and defining a virtual channel within each link that joins the trunk nodes.
However, the above-described prior art has several problems as described herein below.
In a method in which bandwidth is reserved between subscribers by using RSVP, determination of whether a bandwidth is assigned or not is realized on the subscriber""s server and thus cannot be managed on the network side. As a result, there is the problem that, even if it is desired, a particular subscriber cannot reserve network resources such as the bandwidth of a transmission line if the resources are already reserved by another subscriber.
Moreover, a fee-charging service has been difficult to establish using RSVP because authority such as bandwidth management is entrusted to subscribers. Due to the above-described points, RSVP has been difficult to use as a protocol for bandwidth reservation in a public network or carrier network.
Reserved bandwidths can be managed on the network side by a method that uses ATM, but the number of virtual channels to be processed increases at higher-ranking trunk nodes such as trunk nodes 70 and 80 in FIG. 1 where multiple virtual channels are concentrated. This gives rise to the problem of higher costs of the system because intelligent, high-performance trunk nodes are required at higher-ranking trunk nodes where the number of virtual channels increases for the purpose of setting, managing and bandwidth-guaranteeing processes of guaranteed bandwidths. Furthermore, the number of subscriber nodes becomes limited as the number of virtual channels increases. A concrete explanation of this limitation on the number of subscriber nodes follows herein below.
FIG. 2 is a block diagram showing an interface of the prior art that includes a peak-rate bandwidth control capability. Data in which the virtual channel number and reserved bandwidth value are placed in correspondence are multiple-recorded in bandwidth control data memory 94. Bandwidth control circuit 92, which has a scheduler capability, accesses bandwidth control data memory 94 and transmission cell buffer 91 in which cells to be transmitted are stored, and transmits by way of transmission interface circuit 93 at the peak rate (maximum bandwidth) set at cells to be transmitted (Refer to section 3.7 of the Users Manual of xe2x80x9cxcexcPD98401 Local ATM SAR Chipxe2x80x9d published by Nippon Electric Corporation).
If the number of virtual channels that can be controlled by bandwidth control circuit 92 is, for example, 32,000, this type of interface can handle communications on the order of 30,000 partner subscriber nodes at subscriber node 10, but at higher-ranking trunk nodes such as trunk nodes 70 and 80, communication can be handled for only about 180 subscriber node pairs, i.e., a number equal to the square root of 32,000, (in the case of a logical mesh). Thus, a significant limit exists for the bandwidth reservation channels on the subscriber nodes.
In addition to the above-described point in methods using ATM, a bandwidth control data memory of large volume becomes necessary as the number of virtual channels increases, and this leads to the problems of both greater size and greater cost of the device.
The first object of the present invention is to provide a bandwidth control method and bandwidth control system that allows the management of bandwidths to be reserved to be performed on the network administration side.
The second object of the present invention is to provide a bandwidth control method and bandwidth control system that allow simple management and setting of guaranteed bandwidths regardless of increases in the number of channels for which bandwidths are to be reserved.
To achieve the above-described objects, the bandwidth control method of the present invention is a bandwidth control method that is carried out in a network in which a plurality of subscriber nodes accommodating a plurality of subscribers are each connected to each other by trunk nodes; and that includes: for the data transfer from subscriber nodes to trunk nodes, setting virtual channels to each of destination subscriber nodes that are relayed by way of the trunk nodes and reserving bandwidths based on the virtual channels; and for the data transfer from trunk nodes to other trunk nodes or to destination subscriber nodes, establishing virtual channel groups according to route by organizing virtual channels that are relayed by the transfer nodes and reserving bandwidths based on the virtual channel groups.
In the above-described cases, the bandwidth control method of the present invention may further include:
between each of the subscriber nodes, setting a maximum bandwidth for each node pair in which one subscriber node is taken as the source and the other is taken as the destination; and
for the data transfer from the source subscriber node to the destination subscriber node, for each of the links from the source subscriber node to a trunk node, between trunk nodes, and from a trunk node the destination subscriber node, setting bandwidths corresponding to the sum of maximum bandwidths of subscriber node pairs through which data transfer is carried out.
In addition, the bandwidth control method of the present invention may further include:
between each of the subscribers, setting maximum bandwidth for each subscriber pair wherein one subscriber is taken as the source and the other is taken as the destination; and
for the data transfer from a source subscriber node to a destination subscriber node, for a link from a source subscriber node to a trunk node, setting bandwidth corresponding to the sum of the maximum bandwidth of the subscriber pair through which data transfer is carried out.
In addition, the bandwidth control method of the present invention may further include giving priority to data transfer from a specific subscriber node for communication having reserved bandwidth during transmission between trunk nodes and from a trunk node to a destination subscriber node. In such cases, for links between trunk nodes and links from trunk nodes to the destination subscriber node, the bandwidth control method of the present invention may further include both setting virtual channels having bandwidths equal to or greater than the sum of communication having reserved bandwidth, and, of communication that uses the virtual channel, giving a low order of priority to communication that loses reserved bandwidth for the purpose of control that gives priority to data transfer from the specific subscriber node.
In addition, the bandwidth control method of the present invention may further include, for links from a subscriber node to a trunk node, assigning a virtual channel to data transfer from a specific subscriber to a subscriber that is accommodated in the same destination subscriber node.
In any of the above-described cases, an a synchronous transfer mode virtual channel may be used as the virtual channel.
To achieve the above-described object, the bandwidth control system of the present invention includes a network in which a plurality of subscriber nodes accommodating a plurality of subscribers are connected to each other by way of trunk nodes; and
subscriber nodes are configured such that virtual channels are set by destination subscriber node and bandwidth is reserved based on the virtual channels, trunk nodes are configured such that virtual channels are organized by route as virtual channel groups and bandwidth is reserved based on the virtual channel groups.
In the above-described case, the bandwidth control system of the present invention may be configured such that a subscriber node includes:
a plurality of subscriber interface circuits that carry out communication with subscribers;
a first trunk circuit that carries out packet communication with a trunk node by setting a virtual channel for each subscriber node through which communication is relayed by way of the trunk node, reserving bandwidth based on the virtual channels, and using corresponding a virtual channel;
a first switch circuit that switches communication connections between the plurality of subscriber interface circuits and between these subscriber interface circuits and the first trunk circuit; and
a first control means that, in addition to controlling communication connections by the switch circuit, manages the virtual channels and sets the capacity of reserved bandwidths;
and the trunk node includes:
a plurality of second trunk circuits that organize by route the virtual channels that are relayed between other trunk nodes or destination subscriber nodes and through that trunk node and make them virtual channel groups, and reserve bandwidth based on the virtual channel groups;
a second switch circuit that switches communication connections between the plurality of second trunk circuits; and
a second control means that, in addition to controlling communication connections by the second switch circuit, manages the virtual channel groups and sets the number of reserved bandwidths.
Further, in this bandwidth control system, the first trunk circuit that makes up a subscriber node may be configured to include:
first storage means in which is stored the maximum bandwidth information of each virtual channel that is set by destination subscriber node; and
virtual channel setting means that sets the virtual channels of the maximum bandwidth information stored in the first storage means;
and the second trunk circuit that makes up trunk nodes may be configured to include:
second storage means in which are stored the maximum bandwidth information of virtual channel groups organized by route; and
virtual channel group setting means that sets virtual channel groups in accordance with the maximum capacity of bandwidths stored in the second storage means.
Furthermore, in this case, the second trunk circuit that makes up the trunk node may also be configured to include:
a distribution means that distributes transmission from a specific subscriber nodes and transmission from other subscriber nodes; and
transmission means that, for transmission that has been distributed at the distribution means, gives priority to transmission from specific subscriber nodes.
In the present invention as described herein above, bandwidths to be reserved can be easily monitored on the network administrator side because bandwidth control is carried out per route between trunk nodes and between a trunk node to destination subscriber nodes.
In addition, in spite of increases in the number of channels for which bandwidth is to be reserved, at least one channel between these nodes is sufficient because bandwidth control is carried out per route between trunk nodes and from trunk nodes to terminating subscriber nodes as described herein above, thereby eliminating limits on the number of subscribers nodes brought about by increase in the number of virtual channels as in the prior art. As a result, there is no need for an intelligent, high-performance trunk node at higher-ranking trunk nodes, and accordingly, there is no cause for a more costly system.
Moreover, as described herein above, since there is no increase in the number of virtual channels between trunk nodes and from trunk nodes to terminating subscriber nodes, there is no need for a large-capacity memory for the volume of bandwidth control data memory, and there is no concern that a device must increase in size or cost.
In the present invention moreover, between each of the various subscribers, maximum bandwidth is set for subscriber pairs wherein one subscriber is designated as the source and the other as the destination, and for the data transfer from a source subscriber node to the destination subscriber node, the bandwidth for links from source subscriber node to a trunk node is set corresponding to the sum of the maximum bandwidths of the subscriber pairs through which data transfer is carried out, and as a result, bandwidth reservation can be realized between subscribers.
As described herein above, the present invention allows the network manager to actively manage, set, and guarantee the setting of bandwidths for links between a subscriber node to a trunk node or from a trunk node to a destination subscriber node, and as a result, in contrast to RSVP, the present invention can be applied to a fee-based service.
Further, because continued transmission at reserved peak rate is rare, unused surplus bandwidths can be assigned for communication for which bandwidths are not reserved, thereby allowing the provision of low fees for non-reserved communication.
Finally, a single virtual channel of reserved bandwidth between trunk nodes or from a trunk node to a destination subscriber node is sufficient, and even if the network scale should become large, limits in the bandwidth reserved channels at subscriber nodes that occurred in examples of the prior art can be eliminated and a small-scale and economical configuration can be provided.
The above and other objects, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate examples of preferred embodiments of the present invention.